Physical parameters exhibited by a woman in labor in the form of uterine contractions are conventionally monitored using a sensor in the form of a tocodynamometer (hereinafter a “toco”), an intrauterine pressure catheter (hereinafter an “IUPC”), or both types of sensors. Ideally, it is desirable to monitor amplitude, frequency and duration of contractions prior to delivery of an infant. Other physical parameters are also monitored using other types of sensors.
Conventional tocos employ a strain gauge mechanism supported within a rigid ring, termed a “guard ring.” Such tocos exhibit very low compliance (e.g., deflection) when the force of a uterine contraction is applied, cannot provide data on contraction intensity, and are susceptible to artifact when employed with certain patient physiologies such as patients with substantial belly fat, or a thin uterus. Further, such conventional tocos are heavy, nondisposable and costly to purchase, on the order of $300 to $500 each, costly to repair, and are specific to a particular manufacture of monitor. In addition, even with proper cleaning procedures, such tocos may present a risk of cross-contamination between patients.
Recently, a low-cost, lightweight, disposable so-called “pneumatic” toco has been developed, which pneumatic toco assertedly equals if not improves the performance of a conventional guard-ring, strain gauge toco. The pneumatic toco, at a cost of under ten dollars ($10), generates an output in the form of pressure differences within a closed interior air volume as varied by uterine contractions acting upon an elastic membrane and as sensed and converted to electrical signals by a pressure transducer at the distal end of a reusable cable in communication with the closed air volume. Such a pneumatic toco and its operation are described in International PCT Publication No. WO 2012/108950, published Aug. 16, 2012, as applied for by the Board of Trustees of the University of Arkansas on behalf of inventors Hari Eswaran, Curtis L. Lowry and James D. Wilson, the disclosure of which publication is hereby incorporated herein in its entirety by this reference.
A highly commercially successful, low cost, disposable intrauterine pressure catheter has been developed and marketed by Clinical Innovations, LLC, of Murray, Utah as the KOALA® intrauterine pressure catheter (IUPC). The KOALA® IUPC employs a closed air volume to measure frequency, duration and intensity of uterine contractions via a pressure transducer at the distal end of a reusable cable assembly sensing pressure differences in the closed air volume. The KOALA® IUPC and its operation are described in U.S. Pat. Nos. 5,951,497; 5,984,879 and 6,231,524, all assigned to the assignee of the present disclosure and the disclosure of each of which patents is incorporated herein in its entirety by this reference. The commercial success of the KOALA® IUPC has been of such magnitude that it is employed in virtually every hospital throughout the United States, as well as enjoying substantial use in Europe.
Other sensing devices using a closed air volume include LATITUDE® esophageal catheters and anorectal catheters, developed and marketed by Clinical Innovations, LLC, of Murray, Utah.
Urodynamic catheters employing a closed air volume are commercially available as T-DOC® air-charged catheters from T-DOC Company, LLC of Wilmington, Del. Pressure differences within the closed air volume are sensed by a pressure transducer at the distal end of a reusable cable. The T-DOC® catheter and its operation are described in U.S. Pat. No. 6,447,462, assigned to the assignee of the present disclosure, the disclosure of which patent is incorporated herein in its entirety by this reference.
It would be desirable, as recognized by the inventors herein, to be able to employ a single, reusable cable to provide input from different disposable sensors to a monitor. However, sensors such as closed air volume sensors, which employ no electrical circuitry in the sensor itself, present challenges in development of a multi-use cable.